If you’ve ever heard the expression “everything old is new again,” you will understand the appeal of garden ollas. These clay pots have been used for garden irrigation since early civilizations, and have become a popular yard and garden tool again. The secret is in how the water is distributed to your plant roots – the clay olla is unglazed, allowing water to seep out into the ground. The suction created by roots allows the plants to soak up the water released by the olla.
Click on any of the questions below to learn more about how ollas work, what you need to know to use them in your own yard and garden, where you can find them in Tucson, and more!
Olla means "pot," and an olla used in the garden is an unglazed pot made from porous clay (usually terracotta) that is buried in the ground and filled with water to irrigate plant roots.
Ollas come in different shapes and sizes. The traditional shape looks like a bulbous jug with a long narrow neck. There are others that look more like a wine bottle and some that come as a ball with a piece of irrigation tubing connected to it that then hooks up to a water reservoir system. There are also a variety of DIY versions.
Because the clay used to make Ollas is porous, the vessel (when buried in the ground and filled with water) will interact with dry soil and release water through a process known as soil moisture tension. When a plant's roots are close to an Olla, and the plant needs water, the roots create suction - also known as capillary action. Think of putting a small straw in a glass of water or a paintbrush in a can of paint. In both cases, the liquid will be pulled up, irrespective of gravity.
Conversely, when the soil is moist, the soil moisture tension decreases (as there is an equilibrium between the moisture of the ground and that of the sides of the Olla). In this case, the water in the Olla stays put and does not drain out into the soil on its own.
And when the soil is super-saturated, like after a big rain, the Olla will start to fill back up from the gravitational pull of the water as it drains into the earth. In this instance the water leaches back through the porous clay wall and into the Olla.
- If you add water-based fertilizer to an olla, you can use up to 50% less with the same results
- Using an olla for irrigation has been traced back to Northern Africa and China - over 4,000 years ago
- Ollas reduce the amount of work required
- Because less water is wasted, you can see a water savings of 50-70% in your garden
- Ollas work for any type of plant and are especially useful for vegetable crops
- They can be a cost-effective alternative to drip irrigation.
- If you don't have an irrigation system, using Ollas means you'll spend less time hand watering (with a garden hose, sprinkler, etc.). Depending on the Ollas' size, you may only need to fill them every 3 – 7 days.
- Life can get hectic (we've all been there!) and watering becomes yet another chore to add to your long list (and, let's be honest, it's easy to forget to water). If your garden uses Ollas, forgetting to water for a day or two won't have as much of a negative impact.
- Because they're made from biodegradable clay, Ollas are environmentally friendly.
- An Olla keeps soil moisture below ground so less water evaporates and more goes to the plant's roots.
- Irrigating with Ollas is a watering solution that’s about as low-tech as it gets so there's less to go wrong, unlike sophisticated electronic devices/systems (if you've ever had an irrigation system stop working without you realizing it, you'll definitely appreciate Ollas!).
- Because Ollas come in different sizes and shapes, they are ideal for container and/or raised bed gardening.
- Roots tend to stay deeper in the soil when plants are watered with Ollas, which helps prevent plant desiccation (drying out).
- Ollas provide a consistent amount of water and so prevent over or under watering, which can cause plant stress that can lead to diseases or death.
- Unlike irrigation tubing, Ollas are less susceptible to animal and insect damage.
- By keeping moisture deeper in the soil, Ollas help prevent weeds because the soil surface stays dry, and weeds need moisture to germinate.
- Ollas help prevent pooling water which can breed insects, like mosquitoes.
- Slugs and snails are attracted to the moist and cool exposed neck of the Olla (versus plants) and are easy to remove/manage.
- Ollas tend to refill themselves when the ground becomes super-saturated (so you don't need to fill them manually after a heavy rainfall).
- Some users experience lusher plants and higher crop yields when using Ollas vs other forms of irrigation.
- Ollas provide a consistent supply of water that helps prevent cracking on tomatoes and melons.
- When water accessibility is limited (for example, at a public use or community garden), using Ollas can make your watering more efficient, cutting down on water lost to runoff and evaporation.
- Ollas are a good choice if running drip irrigation tubing is impractical, too expensive, unsightly, or is a possible tripping hazard.
- Ollas help prevent water runoff and extreme evaporation (this is especially helpful in places like Tucson where drought is a constant concern).
In vegetable gardens with plants that have fibrous root networks (ex. tomatoes, squash, watermelons, chiles, melons, etc.).
To irrigate flower gardens, shrubs, tree saplings or plant material in general.
In planting pots where there is enough room for both the Olla and flowers/vegetables.
Pick the size and shape based on the plants root system. Shallow rooted plants, like leafy vegetables (ex. lettuce) and some herbs will need shorter Ollas so that the water doesn’t drain underneath the roots.
It’s best to have ones that come with a cap. This prevents dirt, debris, insects and the like from falling into the vessel. It also prevents mosquitoes from breeding inside the Olla. If a premade cap is not provided, then a flat rock or some other object to completely cover the fill tube is necessary.
They come in various types (ex. drip irrigation balls, handmade clay pots, DIY – usually terracotta flower pots, bottles, etc.). Choose the Ollas that best suit your planting area and plants.
A simple way to look at this is that an Olla distributes moisture to an area about equal to the radius of the Olla (i.e. the furthest distance from one side of the Olla's outside wall to the other side).
The type of plant and its root system will determine how close you can plant to the Olla. As an example, plants like tomatoes with long root systems can be planted at the maximum moisture edge (outer limit of the radius) and have plenty of room to grow. Smaller plants like lettuce or decorative flowers with less aggressive root systems need to be planted closer to the Olla.
There is no exact science as to the perfect distance for each plant. Part of the process of successfully growing plants using Ollas is trying different distances. Just remember the radius rule and do a little research about each plant's root system.
Absolutely! One thing to keep in mind with trees and shrubs is that they have both woody and non-woody roots. As the woody roots make their way to the Olla (this may take a year or more) they can encircle the Olla and eventually crack/crush it.
A way to help prevent this is to inspect the root zone around the Olla. This can be done with some very gentle hand excavation to dig away the soil from the outside of the Olla. If you see woody roots starting to make their way around the Olla, it’s time to pull the Olla out of the ground and use it somewhere else. The tree or shrub root system should be well established at this point and only need watering based on the type of plant, soil type, soil moisture, and time of year.
Whether or not an Olla can be left in the ground all year really depends on where you live. Here in Tucson, it’s fine to leave them in the ground all year. But for locations where the ground freezes solid, it’s a good idea to dig them up for the winter.
If you take them out of the ground for the winter, store them in a dry place and make sure that they are empty. It’s also a good idea to wash out any debris that may have accumulated inside the Olla and scrub any dirt off the outside. Now you’re ready to start afresh the following growing season.
That depends. If floating objects like leaves, twigs, mulch chips, etc. have fallen in, then overfill the Ollas until these objects float to the surface. Then skim them off. If dirt and debris sinks to the bottom of the Olla, than the best way to clean it is to remove the Olla from the ground and wash it out with a garden hose. While you’re at it, use a scrub brush on the outside to clean any dirt and debris.
If you have water that is high in mineral content (like calcium here in Tucson) then cleaning your Ollas with a vinegar and water solution is highly recommended. If you want to know when to do it, take a peek inside using a flashlight (when the Olla is empty). If you see evidence of white chips in the bottom or a white lining on the inside walls, then it’s time to clean.
To begin, pop the Olla out of the ground. Clean any debris that might have collected inside. Then mix up a 1:1 vinegar to water solution and pour it into the Olla. Fill it at least to where the neck enters the pot. With the Olla propped up vertically, let the solution do its work. Plan on a wait time of a few hours. Then properly dispose of the water/vinegar solution. And finally, wash the interior of the Olla out with fresh water before burying it in the ground.
Ollas can last for years. But like any product, a little maintenance goes a long way (cleaning, winterizing, etc.).
Ollas can breed mosquitoes if the top is not sealed. Make sure your Ollas have a cover/cap (most commercially manufactured Ollas include one). This will keep not only mosquitoes out, but other things like dirt, mulch, twigs, leaves, slugs, lizards, and even frogs. Also, the lid helps prevent the water from evaporating prematurely.
You’ll see some online videos and writeups about poking a lot of holes in a plastic container, burying it (with the neck poking out above the ground), and filling it with water. This is a slow-release watering system but it does not work like an Olla. These DIY contraptions can distribute water underground and, if properly placed, the water from them can reach the root zone of nearby plants. But the water drains out much faster than an Olla, can go below the root zone quickly, does not operate on the principle of soil moisture tension (which can result in overwatering), the small holes (usually made with an ice pick) tend to clog up with dirt, and they need to be frequently filled.
One of the most common types of DIY Ollas is to glue two (same sized) unglazed terracotta plant pots together. A waterproof material (like a silicone caulk) is used to glue/seal the top rim of each pot together. If your bottom pot has a drainage hole, then it has to be sealed with a waterproof sealant so that water does not run out (or a cork, if you can find out that fits). The top pot also has to have a hole in it – this is where you add the water.
After the glue/sealant dries, make sure that you fill your Olla up with water before you bury it into the ground. You’re checking for leaks.
Next, dig a hole and bury it so that the inverted top pot with the open hole sticks out of the ground a few inches (the majority of the upper pot needs to be buried).
The Olla can be filled with a garden hose, watering can, or whatever you have on hand. Be sure to put a cover over the water fill hole to keep out debris, bugs, mosquitoes, etc., and to prevent the water from evaporating from the fill hole.
There are numerous YouTube videos on the subject of homebuilt Ollas. The one described above seems to be a ubiquitous theme, but there are many other design options to explore. Have fun!
You can buy Ollas right here in Tucson!
EcoSense (sells Dripping Springs Ollas)
4560 N. La Cholla Blvd.
Tucson, AZ 85705
Open Mon., Tues., Fri.: 9 AM – 2 PM
Please call or email to make an appointment (for Covid-19 safety reasons)
- Call-in orders accepted
- Curbside pickup only
Acme Sand & Gravel (sells Dripping Springs Ollas)
7777 E. 22nd St.
Tucson, AZ 85710
Open: Mon. – Fri.: 7 AM – 4 PM / Sat: 7 AM – 2 PM
- Call-in orders accepted or you can pay at their walk-up window (Covid-19 precautions).
EcoGro (sells Cutting Edge Ceramics Ollas)
657 W. Saint Mary’s Road
Tucson, AZ 85701
Open Thurs., Fri., Sat.: 10 AM – 5 PM
- EcoGro sells Cutting Edge Ceramics - Olla Balls, Olla Bottles, and Olla Ball Kits (balls, water reservoir, tubing, etc.). EcoGro will be glad to show you the Cutting Edge Ceramics product line by bringing samples to you outside their store or to your car (provided that you are wearing a Covid mask).
- Curbside pickup only
Payment by phone or at the nursery
Mesquite Valley Growers Nursery (sells Dripping Springs Ollas)
8005 E. Speedway Blvd.
Tucson, AZ 85710
https://www.facebook.com/mesquitevalleygrowersnursery/ (Facebook listing no website)
Open every day: 8:00 AM – 5:00 PM
- Store fully open
- Wear a mask
Depending on the style, construction, and the volume of water held - manufactured Ollas range in price from under $10 and can exceed $200 (ex. a full-blown kit with 25 Olla Balls, a 5-gallon reservoir bucket/with float valve, 25’ of ½” poly tubing, etc.). It also depends on how many are needed for your planting area. They are ideal for gardening on smaller plots of land, in raised beds, and in containers.
For larger landscapes/gardening areas it comes down to personal choice whether to use them exclusively or supplement them with other forms of irrigation.
Ready to Get Started With Ollas?
As you can see above, garden ollas may have been an early invention, but they are still useful today. They are especially helpful in a location like Tucson, where rain has been sparse for several years. We hope you have enjoyed learning about these clay watering tools. If you end up making or using a garden olla, let us know how you like using it in our Tucson Yard & Garden Resources Facebook Group.